how can i control starting point of particles?
Particle-duplicated objects will be centered on their origin points, also known as pivot points. You can move an object's vertices with respect to the origin point in edit mode by selecting all vertices and moving them until you have them where you want them in relation to the pivot.

Another option in object mode is to move the pivot with the options shown in Object > Transform > ... (I frequently use "Origin to 3D Cursor" and "Origin to Geometry.")